1. Field of the Invention
The present invention relates to catheter devices and systems for continuous chemical analysis of body fluids, and in particular, relates to a catheter which may be inserted into the fluid carrying members of a living being for long periods of time to provide a continuous fluid flow for analysis.
2. Description of the Prior Art
The analysis of body fluids is of great importance in medical diagnostics. Up until the present time it was necessary to obtain samples of the body fluids such as, for example, blood, urine, gastric juices, etc., which were prepared and analyzed for their content of certain substances. This technique has the disadvantage of being discontinuous so that the results of the analysis only represented an instantaneous recording at the moment when the samples were taken. Where rapid changes in the samples were occurring, with the passing of time, many samples were required to be taken and analyzed at frequent intervals. This required large amounts of manual labor and placed an unnecessary strain on the patient.
For these and other reasons it has been a goal of the medical profession to devise a method to provide a continuous measurement technique. This technique requires the removal of the relevant fluids from the body with the aid of a catheter, analyzing it and subsequently returning it into the body. Returning the the fluid back into the body, of course, is only possible under certain conditions; for example, blood must be heparinized in order to prevent coagulation. Other body fluids may be influenced by the analysis so they may not be suitable for returning into the body without taking certain precautions. In some cases it may be possible to utilize a substitute or replacement fluid to replace that which was taken out of the body.
Since macromolecular (high molecular weight) and corpuscular components of the body fluid often interfere with the analysis, the latter must be removed before measurement. For this purpose, dialysis and ultrafiltration have proved to be successful. These techniques have been described by O. Aziz and R. Dennhardt in an article entitled Ultrafiltration of Circulating Blood in Vivo. Pflugers Archive, Volume 341 (1973), page 347; and by D. Sailer, G. Berg and F. Matzkies in an article entitled Zur kontinuierlichen Glukosevestimnung in Vivo. Biomed. Technik, Volume 19 (1974), page 134.
Nevertheless, the continuous removal of blood and other body fluids represents a large burden for the patient.